ValueTuple<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12>

// 12 items in a value: Item1…Item12, which can be changed.
public struct System.ValueTuple<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12> : System.IToString, System.IHashable<System.ValueTuple<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12>>
{
    field Item1: T1
    field Item2: T2
    field Item3: T3
    field Item4: T4
    field Item5: T5
    field Item6: T6
    field Item7: T7
    field Item8: T8
    field Item9: T9
    field Item10: T10
    field Item11: T11
    field Item12: T12
    constructor ValueTuple(Item1: T1, Item2: T2, Item3: T3, Item4: T4, Item5: T5, Item6: T6, Item7: T7, Item8: T8, Item9: T9, Item10: T10, Item11: T11, Item12: T12)
    // The same items in a Tuple (a class).
    method ToTuple() -> System.Tuple<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12>
    method ToString() -> System.String<u8>
    method Hash() -> u64
    method Equals(other: System.ValueTuple<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12>) -> bool
}